A typical low voltage power cable is constructed of metal conductors insulated with a polymeric material. These elements are generally twisted to form a core and are protected by another polymeric sheath or jacket material. In certain cases, added protection is afforded by inserting a wrap between the core and the sheath.
In order to have the low voltage power cable approved by the Underwriters Laboratories, the insulation must pass a stringent test with regard to its long term "wet" electrical properties at an elevated temperature under a specified electrical stress, e.g., a temperature of 75.degree. C. at a stress of 600 volts per 15 or 45 mil layer. The term or period of time for immersion in water is a minimum of 12 weeks. The test is described in Underwriters Laboratories 83 (UL-83), Tenth Edition, revision dated Sep. 25, 1991, paragraphs 30.1 to 30.4.
It will be apparent to those skilled in the art that insulation meeting this severe test is decidedly more capable of successfully dealing with wet applications than those highly filled cables which have a tendency, when exposed to water, to increase charge species movement, i.e., conductivity, within the polymer structure thus lowering insulation resistance (IR). It is expected, however, that the cable will not only meet the UL-83 test, but the UL-44 requirements as well provided that the cable is crosslinked. Good flame retardance, low smoke, low corrosivity, and low toxicity add to the industrial requirements for low voltage power cable, which will be exposed to aggravated water conditions.